DIY Projects

Adding a Built-in Sandbox to a Wood Deck

By: Danny Lipford

Child playing in competed wood deck sandbox.

While a built-in sandbox can be added to an existing wood deck, it’s much easier to add it when constructing a new deck. Here’s how to go about adding a sandbox to your deck.

How to add a sandbox to a wood deck:

  1. Start by deciding on the size and location of the sandbox. We made our sandbox 3’ x 3’ and located it in an outside corner of the deck.
  2. Construct a four-sided box for the sandbox using the same materials as the deck floor joists. We made our box from 2×6 pressure treated lumber.
  3. Attach the bottom boards to the sandbox with long deck screws leaving a gap between each board for drainage. We used 5/4” deck boards for the bottom, but you should use 2” lumber for a larger sandbox.
  4. To define the space for the sandbox, a 2×6 was run from the outer band joist to the floor joist next to the sandbox.
  5. To allow room for the deck railing, we attached 4×4 blocks to the outer band joists as spacers.
  6. Attach the sandbox to the spacers and joists using long deck screws or nuts and bolts.
  7. For additional support, attach a 2×6 across the bottom of the sandbox perpendicular to the bottom boards, and support it from the ground with a 4×4 post.
  8. Make a cover for the sandbox from 5/4” decking, cutting a notch in one side for easy opening.
  9. Line the sandbox with landscape fabric, and fill with sand.

Framing for wood deck sandbox.

Watch this video to find out more.

Further Information

Print   Video Transcript

Danny Lipford: Building a sandbox into the surface of a deck is a great way to include children in the entertaining aspect of an outdoor space.

Begin by identifying the location and size of the sandbox. Construction of the deck will proceed normally until you begin adding the joists. The joists can be installed everywhere except where the sandbox will be located because you will build and install it before completing the joist system.

The walls of the box are created using the same materials as the joists. In this case two-by-sixes. We’re making ours a three-foot by three-foot square.

Once the perimeter of the box is complete, you can add the bottom. We’re using five-quarter deck boards for this, but you would want to use two-by stock for anything larger.

We’re attaching the boards to the bottom of the box with deck screws, leaving small spaces between the boards for water to drain through. Later we’ll wrap the inside of the box with landscape fabric to prevent the sand from sifting out.

We’re spacing our box three and a half inches from the edges of the deck in a corner, so we’re attaching four-by-four blocks to the inside of those two edges, then attaching the box to the blocks. Nails will hold them in place, but be sure to follow up with long lag screws to help carry the weight.

Next, we’re adding a two-by-six running from the band joist on the edge, along the back edge of the sandbox to the nearest joist on the other side. Then we add another two-by-six between that piece and the band joist on the other side. Again, nails are fine for positioning, but you’ll want to use lag screws to secure them permanently.

Now you can finish running joists from the sandbox to the band joist behind it. For additional support we added a two-by-six support directly below the box, running down to the ground. The landscape fabric in the box next using galvanized staples.

When the decking reaches the sandbox, mark and cut the boards to end an inch or so from the inside edge of the box. That lip will support the cover you’ll build next to cover the sandbox when it’s not in use. In our case the cover is six deck boards wide.

We’ll cut them about an eighth of an inch less than the opening, and we’re squaring up the ends so they form a nice straight line. Then we’re attaching two-by-twos to hold the boards together.

On one side the two-by-twos extend past the edge. When the cover is complete, these pieces hook under the deck to position the cover. A notch cut from the deck on the opposite side allows you to slip your hand into it and lift it up when the sand box is in use.



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